Two Proofs of Halpern-L\"auchli Theorem
数学专题报告
报告题目(Title)：Two Proofs of Halpern-L\"auchli Theorem
报告人(Speaker)：杨跃 教授（National University of Singapore）
地点(Place)：教八楼401
时间(Time)：2025年10月21日（周二）13:30-14:30
邀请人(Inviter)：施翔晖
报告摘要
I will present two proofs of Halpern-L\"auchli Theorem (HL). One is elementary and can be carried out within RCA$_0$ plus $\Sigma^0_3$-induction. This elementary proof is part of an ongoing project with Chong Chitat and Li Wei, aiming to find the proof-theoretic strength of HL. The other is a forcing proof, following a presentation by Dobrinen. The proof is highly nontrivial and offers a sharp contrast of the elementary proof.
